Methods of preparing an intermediate oxidation product from a hydrocarbon by utilizing an activated initiator

ABSTRACT

Methods for oxidizing a hydrocarbon to an intermediate oxidation product by utilizing an activated initiator. The initiator is activated by partially oxidizing a first mixture of the initiator and a hydrocarbon, which mixture contains a rather large amount of initiator. The first mixture may even be just initiator. The first mixture, after the partial oxidation, is mixed with a second mixture containing hydrocarbon and a smaller amount of initiator. The second mixture may even contain no initiator at all. The oxidation is continued to a desired degree. Preferably, at least one of the two mixtures, and even more preferably both reaction mixtures contain an oxidation catalyst and an acidic solvent.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. Provisional Application No.60/032,437, filed Dec. 18, 1996, which application is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

This invention relates to methods of making intermediate oxidationproducts, and preferably dibasic acids, such as adipic acid for example,by oxidizing a hydrocarbon, such as cyclohexane for example, with a gascontaining an oxidant, preferably oxygen.

BACKGROUND OF THE INVENTION

There is a plethora of references (both patents and literature articles)dealing with the formation of intermediate oxidation products, such asdiacids, for example, one of the most important being adipic acid.Adipic acid is used to produce Nylon 66 fibers and resins, polyesters,polyurethanes, and miscellaneous other compounds.

There are different processes of manufacturing intermediate oxidationproducts, such as adipic acid for example. The conventional processinvolves a first step of oxidizing cyclohexane with oxygen to a mixtureof cyclohexanone and cyclohexanol (KA mixture), and then oxidation ofthe KA mixture with nitric acid to adipic acid. Other processes include,among others, the "Hydroperoxide Process," the "Boric Acid Process," andthe "Direct Synthesis Process," which involves direct oxidation ofcyclohexane to adipic acid with oxygen in the presence of solvents,catalysts, and initiators or promoters.

Initiators or promoters are presently being used to shorten considerablyan induction period at the beginning of the reaction. Acceptedexplanations, which have been given regarding the role of the initiatorsor promoters, involve oxidation of the catalyst, which is usuallycobaltous ions to cobaltic ions.

The Direct Synthesis Process has been given attention for a long time.However, to this date it has found little commercial success. One of thereasons is that although it looks very simple at first glance, it isextremely complex in reality. Due to this complexity, one can findstrikingly conflicting results, comments, and views in differentreferences.

It is well known that after a reaction has taken place according to theDirect Synthesis, a mixture of two liquid phases is present at ambienttemperature, along with a solid phase mainly consisting of adipic acid.The two liquid phases have been called the "Polar Phase" and the"Non-Polar" phase. However, no attention has been paid so far to theimportance of the two phases, except for separating the adipic acid fromthe "Polar Phase" and recycling these phases to the reactor partially ortotally with or without further treatment. Further, no attention hasbeen paid to the behavior of catalyst, such as solubility, for example,during reaction conditions.

It is also important to note that most, if not all, studies on theDirect Synthesis Process have been conducted in a batch mode, literallyor for all practical purposes.

There is a plethora of references dealing with oxidation of organiccompounds to produce acids, such as, for example, adipic acid.

The following references, among the plethora of others, may beconsidered as representative of oxidation processes relative to thepreparation of diacids.

U.S. Pat. No. 5,463,119 (Kollar) discloses a process for the oxidativepreparation of C₅ -C₈ aliphatic dibasic acids by

(1) reacting,

(a) at least one saturated cycloaliphatic hydrocarbon having from 5 to 8ring carbon atoms in the liquid phase and

(b) an excess of oxygen gas or an oxygen-containing gas in the presenceof

(c) a solvent comprising an organic acid containing only primary and/orsecondary hydrogen atoms and

(d) at least about 0.002 mole per 1000 grams of reaction mixture of apolyvalent heavy metal catalyst;

(2) removing the aliphatic dibasic acid; and

(3) recycling intermediates, post oxidation components, and derivativesthereof remaining after removal of the aliphatic dibasic acid into theoxidation reaction.

U.S. Pat. No. 5,374,767 (Drinkard et al.) discloses formation ofcyclohexyladipates in a staged reactor, e.g., a reactive distillationcolumn. A mixture containing a major amount of benzene and a minoramount of cyclohexene is fed to the lower portion of the reaction zoneand adipic acid is fed to the upper portion of the reaction zone,cyclohexyladipates are formed and removed from the lower portion of thereaction zone and benzene is removed from the upper portion of thereaction zone. The reaction zone also contains an acid catalyst.

U.S. Pat. No. 5,321,157 (Kollar) discloses a process for the preparationof C₅ -C₈ aliphatic dibasic acids through oxidation of correspondingsaturated cycloaliphatic hydrocarbons by

(1) reacting, at a cycloaliphatic hydrocarbon conversion level ofbetween about 7% and about 30%,

(a) at least one saturated cycloaliphatic hydrocarbon having from 5 to 8ring carbon atoms in the liquid phase and

(b) an excess of oxygen gas or an oxygen containing gas mixture

in the presence of

(c) less than 1.5 moles of a solvent per mole of cycloaliphatichydrocarbon (a), wherein said solvent comprises an organic acidcontaining only primary and/or secondary hydrogen atoms and

(d) at least about 0.002 mole per 1000 grams of reaction mixture of apolyvalent heavy metal catalyst; and

(2) isolating the C₅ -C₈ aliphatic dibasic acid.

U.S. Pat. No. 5,221,800 (Park et al.) discloses a process for themanufacture of adipic acid is disclosed. In this process, cyclohexane isoxidized in an aliphatic monobasic acid solvent in the presence of asoluble cobalt salt wherein water is continuously or intermittentlyadded to the reaction system after the initiation of oxidation ofcyclohexane as indicated by a suitable means of detection, and whereinthe reaction is conducted at a temperature of about 50° C. to about 150°C. at an oxygen partial pressure of about 50 to 420 pounds per squareinch absolute.

U.S. Pat. No. 3,987,100 (Barnette et al.) describes a process ofoxidizing cyclohexane to produce cyclohexanone and cyclohexanol, saidprocess comprising contacting a stream of liquid cyclohexane with oxygenin each of at least three successive oxidation stages by introducinginto each stage a mixture of gases comprising molecular oxygen and aninert gas.

U.S. Pat. No. 3,957,876 (Rapoport et al.) describes a process for thepreparation of cyclohexyl hydroperoxide substantially free of otherperoxides by oxidation of cyclohexane containing a cyclohexane solublecobalt salt in a zoned oxidation process in which an oxygen containinggas is fed to each zone in the oxidation section in an amount in excessof that which will react under the conditions of that zone.

U.S. Pat. No. 3,932,513 (Russell) discloses the oxidation of cyclohexanewith molecular oxygen in a series of reaction zones, with vaporizationof cyclohexane from the last reactor effluent and parallel distributionof this cyclohexane vapor among the series of reaction zones.

U.S. Pat. No. 3,530,185 (Pugi) discloses a process for manufacturingprecursors of adipic acid by oxidation with an oxygen-containing inertgas which process is conducted in at least three successive oxidationstages by passing a stream of liquid cyclohexane maintained at atemperature in the range of 140° C. to 200° C. and a pressure in therange of 50 to 350 p.s.i.g. through each successive oxidation stage andby introducing a mixture of gases containing oxygen in each oxidationstage in an amount such that substantially all of the oxygen introducedinto each stage is consumed in that stage thereafter causing theresidual inert gases to pass countercurrent into the stream of liquidduring the passage of the stream through said stages.

U.S. Pat. No. 3,515,751 (Oberster et al.) discloses a process for theproduction of epsilon-hydroxycaproic acid in which cyclohexane isoxidized by liquid phase air oxidation in the presence of a catalyticamount of a lower aliphatic carboxylic acid and a catalytic amount of aperoxide under certain reaction conditions so that most of the oxidationproducts are found in a second, heavy liquid layer, and are directed tothe production of epsilon-hydroxycaproic acid.

U.S. Pat. No. 3,361,806 (Lidov et al.) discloses a process for theproduction of adipic acid by the further oxidation of the products ofoxidation of cyclohexane after separation of cyclohexane from theoxidation mixture, and more particularly to stage wise oxidation of thecyclohexane to give high yields of adipic acid precursors and also toprovide a low enough concentration of oxygen in the vent gas so that thelatter is not a combustible mixture.

U.S. Pat. No. 3,234,271 (Barker et al.) discloses a process for theproduction of adipic acid by the two-step oxidation of cyclohexane withoxygen. In a preferred embodiment, mixtures comprising cyclohexanone andcyclohexanol are oxidized. In another embodiment, the process involvesthe production of adipic acid from cyclohexane by oxidation thereof,separation of cyclohexane from the oxidation mixture and recyclethereof, and further oxidation of the other products of oxidation.

U.S. Pat. No. 3,231,608 (Kollar) discloses a process for the preparationof aliphatic dibasic acids from saturated cyclic hydrocarbons havingfrom 4 to 8 cyclic carbon atoms per molecule in the presence of asolvent which comprises an aliphatic monobasic acid which contains onlyprimary and secondary hydrogen atoms and a catalyst comprising a cobaltsalt of an organic acid, and in which process the molar ratio of saidsolvent to said saturated cyclic hydrocarbon is between 1.5:1 and 7:1,and in which process the molar ratio of said catalyst to said saturatedcyclic hydrocarbon is at least 5 millimoles per mole.

U.S. Pat. No. 3,161,603 (Leyshon et al.) discloses a process forrecovering the copper-vanadium catalyst from the waste liquors obtainedin the manufacture of adipic acid by the nitric acid oxidation ofcyclohexanol and/or cyclohexanone.

U.S. Pat. No. 2,565,087 (Porter et al.) discloses the oxidation ofcycloaliphatic hydrocarbons in the liquid phase with a gas containingmolecular oxygen and in the presence of about 10% water to produce twophases and avoid formation of esters.

U.S. Pat. No. 2,557,282 (Hamblet et al.) discloses production of adipicacid and related aliphatic dibasic acids; more particularly to theproduction of adipic acid by the direct oxidation of cyclohexane.

U.S. Pat. No. 2,439,513 (Hamblet et al.) discloses the production ofadipic acid and related aliphatic dibasic acids and more particularly tothe production of adipic acid by the oxidation of cyclohexane.

U.S. Pat. No. 2,223,494 (Loder et al.) discloses the oxidation of cyclicsaturated hydrocarbons and more particularly to the production of cyclicalcohols and cyclic ketones by oxidation of cyclic saturatedhydrocarbons with an oxygen-containing gas.

U.S. Pat. No. 2,223,493 (Loder et al.) discloses the production ofaliphatic dibasic acids and more particularly to the production ofaliphatic dibasic acids by oxidation of cyclic saturated hydrocarbonswith an oxygen-containing gas.

German Pat. No. DE 44 26 132 A 1 (Kysela et al.) discloses a method fordehydration of process acetic acid from the liquid-phase oxidation ofcyclohexane with air, in the presence of cobalt salt as a catalyst afterseparation of the adipic acid by filtration and the cyclohexane phase byphase separation, while simultaneously avoiding cobalt salt precipitatesin the dehydration column, characterized in that the acetic acid phaseto be returned to the beginning of the process is subjected toazeotropic distillation by the use of added cyclohexane, underdistillative removal of the water down to a residual content of lessthan about 0.3 to 0.7 wt %.

PCT Demand International publication WO 96/03365 (Costantini et al.)discloses a method of recycling a cobalt-containing catalyst in areaction involving the direct oxidation of cyclohexane into adipic acidusing an oxygen containing gas. The method is characterized in that thereaction mixture, obtained in a preceding stage where the cyclohexanewas oxidized into adipic acid, of which at least part of theintermediate oxidation products, such as cyclohexanol and cyclohexanone,the carboxylic acid and water has been separated and of which at leastpart of the adipic acid formed has been recovered by crystallization,undergoes at least one extraction operation using at least oneco-solvent or a mixture comprising a co-solvent and a carboxylic acid.The method is also characterized by the separation of a mixturecontaining at least part of the cobalt catalyst, part of the carboxylicacid and optionally residual quantities of other compounds and asolution containing the co-solvent and at least part of the glutaric andsuccinic acids formed during the oxidation reaction, and the carboxylicacid.

None of the above references, or any other references known to theinventors disclose, suggest or imply, singly or in combination,oxidation of hydrocarbons to intermediate oxidation products, such asmonobasic acids, dibasic acids, etc., in the presence of an activatedinitiator, subject to the intricate and critical controls andrequirements of the instant invention as described and claimed.

Our U.S. Pat. Nos. 5,580,531, 5,558,842, 5,502,245, and our co-pendingapplications 08/477,195 (filed Jun. 7, 1995), 08/587,967 (filed Jan. 17,1996), and 08/620,974 (filed Mar. 25, 1996), now U.S. Pat. No.5,654,475, all of which are incorporated herein by reference, describemethods and apparatuses relative to controlling reactions in atomizedliquids.

Our co-pending application, Docket No. T-603, of Mark W. Dassel,Eustathios Vassiliou, David C. DeCoster, Ader M. Rostami, and Sharon M.Aldrich, titled "Methods and Devices for Controlling the Reaction Rateof a Hydrocarbon to an Acid by Making Phase-related Adjustments," filedon Mar. 6, 1997, and having a Ser. No. 08/812,847, is also incorporatedherein by reference.

Our co-pending application, Docket No. T-701, of Mark W. Dassel, DavidC. DeCoster, Ader M. Rostami, Sharon M. Aldrich, and EustathiosVassiliou, titled "Methods and Devices for Preparing Dibasic Acids,"filed on Mar. 27, 1997, and having a Ser. No. 08/824,992, is alsoincorporated herein by reference.

All of the following patent applications, which were filedsimultaneously with the present application are also incorporated hereinby reference:

Docket No. U.S. patent application Ser. No. 08/859,985 of EustathiosVassiliou, Mark W. Dassel, David C. DeCoster, Ader M. Rostami, andSharon M. Aldrich, titled "Methods and Devices for Controlling theReaction Rate of a Hydrocarbon to an Intermediate Oxidation Product byPressure Drop Adjustments";

Docket No. U.S. patent application Ser. No. 08/861,281 of Mark W.Dassel, Eustathios Vassiliou, David C. DeCoster, Ader M. Rostami, andSharon M. Aldrich, titled "Methods and Devices for Controlling theReaction Rate of a Hydrocarbon to an Intermediate Oxidation Product byMonitoring Flow of Incoming and Outcoming Gases";

Docket No. U.S. patent application Ser. No. 08/861,180 of David C.DeCoster, Ader M. Rostami, Mark W. Dassel, and Eustathios Vassiliou,titled "Methods and Devices for Controlling the Oxidation Rate of aHydrocarbon by Adjusting the Ratio of the Hydrocarbon to aRate-Modulator";

Docket No. U.S. patent application Ser. No. 08/859,890 of Ader M.Rostami, Mark W. Dassel, Eustathios Vassiliou, David C. DeCoster, titled"Methods and Devices for Controlling the Oxidation of a Hydrocarbon toan Acid by Regulating Temperature/Conversion Relationship in Multi-StageArrangements"; and

Docket No. U.S. patent application Ser. No. 08/861,210 of EustathiosVassiliou, Ader M. Rostami, David C. DeCoster, and Mark W. Dassel,titled "Pseudo-Plug-Flow Reactor."

SUMMARY OF THE INVENTION

As aforementioned, this invention relates to methods of makingintermediate oxidation products by oxidizing a hydrocarbon with a gascontaining an oxidant, preferably oxygen. More particularly, it relatesto a method of preparing an intermediate oxidation product from ahydrocarbon comprising the steps of:

(a) feeding a hydrocarbon and an initiator into a first reaction zone ata first hydrocarbon to initiator ratio by weight;

(b) oxidizing partially at least one of said hydrocarbon and initiatorto form a first mixture;

(c) mixing the first mixture with a second mixture comprising the samehydrocarbon and initiator, the hydrocarbon and the initiator of thesecond mixture being present at a second hydrocarbon to initiator ratioby weight higher than the first hydrocarbon to initiator ratio;

(d) further oxidizing said hydrocarbon to a desired degree.

At least one of steps (c) and (d) may be conducted in a second reactionzone different than the first reaction zone, or at least one of steps(b), (c), and (d) may be conducted in the first reaction zone. Thus, inthis method, just one reaction zone may be used or more than onereaction zones.

Preferably, the method comprises a step of introducing into at least oneof the first and the second reaction zone at least one ingredientselected from a group consisting of solvent and catalyst. The solventpreferably comprises an acid, and more preferably acetic acid. Thecatalyst preferably comprises a cobalt compound, and more preferablycobalt acetate.

Preferably, the first hydrocarbon to initiator ratio is in the range of0/1 to 50/1, and the second hydrocarbon to initiator ratio is in therange of 10/1 to 1000/1, provided as aforementioned that the firsthydrocarbon to initiator ratio is lower than the second hydrocarbon toinitiator ratio.

The initiator may preferably be a ketone, the ketone corresponding to anoxidation product of the hydrocarbon, or it may be an aldehyde, thealdehyde being a reduction product of the acid. For example if thehydrocarbon is cyclohexane, it is preferable that the initiator iscyclohexanone. Similarly, if the acid is acetic acid the initiator maybe acetaldehyde. If the hydrocarbon is cyclohexane and the acid isacetic acid, the initiator may preferably be either cyclohexanone oracetaldehyde or a combination thereof. However, it is preferable that itis cyclohexanone.

The processes of the instant invention are particularly suited in thecase that the hydrocarbon comprises cyclohexane, the intermediateoxidation product comprises adipic acid, the initiator comprisescyclohexanone, the solvent comprises acetic acid, and the catalystcomprises a cobalt compound.

Preferably, the first mixture and the second mixture are mixed at afirst mixture to second mixture ratio (third ratio) in the range of 1/5to 1/500, more preferably in the range of 1/10 to 1/200, and even morepreferably in the range of 1/20 to 1/100. Preferably, the conversion ofhydrocarbon and initiator to all oxidation products, in the first zone,is maintained in the range of 5-90%, more preferably in the range of10-80%, and even more preferably in the range of 20-60%.

This arrangement of the instant invention, may substantially eliminatethe initiation delay, while providing good selectivity and yield.

In a different example, the hydrocarbon may be an aromatic compoundhaving methyl groups. The aromatic compound preferably comprises amoiety selected from a group consisting of toluene, o-xylene, p-xylene,m-xylene and a mixture thereof, and the intermediate oxidation productcomprises a moiety selected from a group consisting of benzoic acid,phthalic acid, isophthalic acid, terephthalic acid, and a mixturethereof.

Further, the instant invention pertains to a method, wherein theintermediate oxidation product comprises a compound selected from agroup consisting of adipic acid, phthalic acid, isophthalic acid, andterephthalic acid, and the method further comprises a step of reactingsaid intermediate oxidation product with a third reactant selected froma group consisting of a polyol, a polyamine, and a polyamide in a mannerto form a polymer of a polyester, or a polyamide, or a (polyimide and/orpolyamideimide), respectively.

The method may further comprise a step of spinning the polymer intofibers.

BRIEF DESCRIPTION OF THE DRAWING

The reader's understanding of this invention will be enhanced byreference to the following detailed description taken in combinationwith the drawing figures, wherein:

FIG. 1 illustrates schematically an apparatus in relevance to apreferred embodiment of the present invention.

FIG. 2 illustrates schematically a different apparatus in relevance toanother preferred embodiment of the present invention, whereinatomization is employed.

DETAILED DESCRIPTION OF THE INVENTION

As mentioned earlier, this invention relates to methods of makingintermediate oxidation products, such as acids, for example, byoxidizing a hydrocarbon with a gas containing an oxidant, preferablyoxygen.

The methods of the present invention may be applied preferably to acidsfrom the corresponding hydrocarbons. Examples are formation of adipicacid from cyclohexane, of glutaric acid from cyclopentane, of pimelicacid from cycloheptane, of benzoic acid from toluene, of phthalic acidfrom o-xylene, of isophthalic acid from mxylene, of terephthalic acidfrom p-xylene, and the like. It should be pointed out, however, thatthis invention is not limited to formation of acids, but to intermediateoxidation products different than oxides of carbon. Examples of otherintermediate oxidation products are cyclohexanone, cyclohexanol,cyclohexylhydroperoxide, mixtures thereof, and the like.

As aforementioned, initiators have been used so far to initiate areaction, such as oxidation of cyclohexane to adipic acid, for example.This initiation of reaction or oxidation shortens an induction periodconsiderably. The induction period in their absence is in most occasionsunacceptably long, frequently of the order of days, while in theirpresence, the induction period is rather short, frequently of the orderof a fraction of one hour. The explanation accepted by many researchersis that the initiators induce oxidation of the catalyst, which usuallycomprises cobaltous ions, to cobaltic ions. Cobaltic ions are importantin the mechanism of oxidations, such as the oxidation of cyclohexane toadipic acid for example. After a certain amount of cobaltic ions havebeen formed, the mechanisms proposed involve a combination of cobaltousand cobaltic ions, both of which are considered as being regeneratedthrough formation of intermediate species during the oxidation. Examplesof initiators include but are not limited to acetaldehyde,cyclohexanone, methylethylketone, etc.

According to this invention, the oxidation is initiated in an abundanceof initiator, and then it is continued in the presence of a rather smallamount of initiator, adequate to allow the oxidation to proceed at areasonable rate. When the initiator is in great abundance, the reactionis fast, and if the amount of initiator is high enough the initiationperiod is eliminated for all practical purposes, so that the reactionproceeds immediately. Under conditions, the selectivity and yield ofintermediate oxidation product from the hydrocarbon and/or initiator,may suffer in the first reaction zone. However, by mixing a rather smallamount of the first mixture with a considerably larger amount of thesecond mixture, the overall selectivity and yield (after the hydrocarbonhas been oxidized to the desired degree in the second reaction zone)become insignificant. Preferably, the first mixture and the secondmixture are mixed at a first mixture to second mixture ratio in therange of 1/5 to 1/500, more preferably in the range of 1/10 to 1/200,and even more preferably in the range of 1/20 to 1/100. Preferably, theconversion of hydrocarbon and initiator to all oxidation products, inthe first zone, is maintained in the range of 5-90%, more preferably inthe range of 10-80%, and even more preferably in the range of 20-60%.

This arrangement of the instant invention, may substantially eliminatethe initiation delay, while providing good selectivity and yield. Thetwo steps discussed above may take place in one or in more than onereaction zones.

In most oxidations, according to the present invention, a solvent isinvolved, such as acetic acid for example. If an aldehyde is used as aninitiator, it is preferable that the aldehyde corresponds to the acidused as solvent in the oxidation reaction. If acetic acid is the solventused in the oxidation, for example, acetaldehyde should preferably beused as an initiator. Similarly, if an aldehyde is to be used in anoxidation as an initiator, and if the solvent is propionic acid,propionaldehyde should be preferably utilized. The use of acetic acid assolvent is highly preferred, because it is considerably more stable thanother organic acids. Use of the corresponding aldehyde is preferablebecause if oxidized it turns to the corresponding acid. Thus, ifacetaldehyde is used as an initiator, and if it is oxidized it turns toacetic acid which is the solvent.

In a similar manner, if a ketone is used as the initiator, it ispreferable that the ketone corresponds to the hydrocarbon which is to beoxidized. Thus, for example, in the case that the hydrocarbon to beoxidized to adipic acid is cyclohexane, the preferable ketone to be usedas an initiator should be cyclohexanone. Use of cyclohexanone as aninitiator, in the case of direct synthesis of adipic acid, is ofparticular interest because cyclohexane may initially be partiallyoxidized to form just a small appropriate amount of cyclohexanone, andthen further oxidized to adipic acid.

In FIG. 1, there is depicted a reactor system 10, which may be used forpracticing a preferred embodiment of the instant invention. The reactorsystem 10 comprises an initiator activation chamber 11, which in turncomprises a first reaction zone 13. Feeding lines 15, 17, 19, 21 and 23are connected to the initiator activation chamber 11 for feedinginitiator, hydrocarbon, catalyst, solvent, and oxidant, respectively, tothe first reaction zone 13. Of course, premixing of two or more of theabove ingredients may take place at an earlier stage, and the resultingmixture may be fed to the reaction zone 13 as one stream. An outlet gasline 25 may be used to remove off-gases.

The reactor system 10 also comprises a reaction chamber 12, which inturn comprises a second reaction zone 14. Feeding lines 16, 18, 20, 22and 24 are connected to the reaction chamber 12 for feeding initiator,hydrocarbon, catalyst, solvent, and oxidant, respectively, to the secondreaction zone 14. Of course, premixing of two or more of the aboveingredients may take place at an earlier stage, and the resultingmixture may be fed to the reaction zone 14 as one stream. An outlet gasline 26 may be used to remove off-gases. Transfer line 28 connects theinitiator activation chamber 11 with the reaction chamber 12, and it isused for transferring activated initiator from the initiator activationchamber 11 to the reaction chamber 12. A liquid exit line 30 is alsoconnected to the reaction chamber 12 for removing oxidized substantiallyliquid products from the reaction zone 14.

Miscellaneous accessories, such as for example, temperature measuringand control devices, pressure measuring and control devices, heaters,coolers, heat exchangers, reflux devices, valves, pumps, controllers,feed-back and control lines, oxidation-product treatment devices, andothers, are not shown in FIG. 1 for purposes of clarity and brevity.Examples of such accessories are given in our aforementioned patents andpatent applications.

The initiator activation chamber 11 and/or the reaction chamber 12 maybe of the atomization type, the stirred-tank reactor type, the plug-flowreactor type, or any other suitable type, depending on the individualcircumstances.

In operation of this embodiment, initiator is fed to the activationchamber 11 through feed line 15, and hydrocarbon through feed line 17.The operation of the preferred embodiments of this invention may bebetter understood if it is presented in the form of examples. Forexample, in the case that the hydrocarbon is cyclohexane and theintermediate oxidation product is adipic acid, the initiator, which ispreferably cyclohexanone or acetaldehyde, and more preferablycyclohexanone is introduced through feed line 15, while the hydrocarbon,being in this example cyclohexane is introduced through feed line 17. Itis preferable that a first ratio of the flows of cyclohexane tocyclohexanone fed to the activation chamber 11 is lower than 50 to 1.More preferably, especially in the case that cyclohexanone is used asinitiator, no hydrocarbon is fed into the initiator activation chamber11, thus the first ratio being 0 to 1. In the case of other initiators,such as acetaldehyde for example, it is preferable that at least somehydrocarbon, cyclohexane for example is also fed to the activationchamber 11. It is also preferable that a catalyst, for example cobaltacetate, and a solvent, for example acetic acid, enter the initiatoractivation chamber 11 through feed lines 19 and 21, respectively. Thefeed rate of catalyst is preferably 1 to 20% based on the sum of feedsof catalyst plus initiator plus hydrocarbon plus solvent, by weight, andmore preferably 2 to 10%. The rate of solvent fed should preferably be50 to 90% of the total feed to the initiator activation chamber. Thecatalyst is preferably fed dissolved in the solvent.

Oxidant, which is preferably a gaseous mixture of an inert gas, such asnitrogen for example mixed with oxygen, or just oxygen, enters theinitiator activation chamber 11 through feed line 23. Off gases mayleave the system through outlet line 25. The reaction starts very fast,if not immediately, due to the large amount of initiator present, thussubstantially eliminating any induction period. In the case of adipicacid as the intermediate oxidation product, the temperature ispreferably maintained in the range of 70° C. to 120° C., and morepreferably in the range of 90° C. to 110° C. The partial pressure ofoxygen is preferably maintained in the range of 50 to 500 p.s.i. andmore preferably in the range of 100 to 200 p.s.i.

In sequence, liquid containing partially converted hydrocarbon and/orinitiator is being transferred to the reaction chamber 12 throughtransfer line 28 at a desired flow rate, and it is mixed in the secondreaction zone 14 with additional hydrocarbon entering the secondreaction zone 14 through feed line 18. Additional initiator, catalystand solvent may enter the reaction zone 14 of the reaction chamber 12through feed lines 16, 20, and 22, respectively, if so desired. It iscritical that the first ratio of hydrocarbon to initiator entering thereaction zone 11 through lines 17 and 15, respectively, is lower thansecond ratio of hydrocarbon to initiator entering the reaction zone 14through feed lines 18 and 16, respectively. All the ingredients beingfed to the reaction zone 14 are eventually mixed, and the hydrocarbon isoxidized by oxidant (preferably oxygen or a mixture of oxygen and inertgas) entering the reaction zone 14 through feed line 24. The oxidized(to a desired degree) hydrocarbon leaves the reaction zone 14 of thereaction chamber 12 through liquid exit line 30 for separation of theintermediate product (adipic acid in this example), and furthertreatment for removal of by-products, recycling unreacted matter, andthe like. Continual or periodic analysis of the contents of the tworeaction zones assists in achieving good control of the process.

Pressures and temperatures in the second reaction zone may be the sameor different than the ones prevailing in the first reaction zone.

It is highly preferable, at least in the case that the hydrocarbon iscyclohexane, the initiator is cyclohexanone, and the intermediateoxidation product is adipic acid, to feed no hydrocarbon in the firstreaction zone 13, and to feed no additional initiator in the secondreaction zone 14.

The operations performed in the activation chamber 11 and the reactionchamber 12, may be conducted in the reaction chamber 12, in the case ofa batch system for example. According to this embodiment, the activationchamber 11 and the transfer line 28 are omitted. Initially, initiatorand hydrocarbon are added to the chamber, preferably in an abundance ofinitiator, and an oxidation is initiated to a desired low degree ofconversion. Catalyst and initiator are preferably also added. When thistask is performed, a mixture is produced in the reaction zone 14, havingan excess of hydrocarbon as compared to the initial mixture, by feedingdesired amounts of initiator, hydrocarbon, catalyst and solvent throughfeed lines 16, 18, 20, and 22, respectively. The oxidation of thehydrocarbon is continued to a desired degree, and the contents of thereaction chamber 12 are released through line 30 for further treatment,recycling, etc.

In still another embodiment of the instant invention, better illustratedin FIG. 2, there is provided an atomization reaction chamber 112, whichincludes a first reaction zone 114. There are also provided feed lines115, 117, 119, and 121, for feeding initiator, hydrocarbon, catalyst,and solvent, respectively. These lines merge to a first mixture feedline 132, which in turn leads to a first sprayer or atomizer. Similarly,there are further provided feed lines 116, 118, 120, and 122 for feedinginitiator, hydrocarbon, catalyst, and solvent, respectively. These linesmerge to a second mixture feed line 134, which in turn leads to a secondsprayer 138.

Intermediate vessels, heaters, other elements mentioned hereinabove,etc. which may be used as linkages from individual feed lines to themixture feed lines are not shown for purposes of clarity and brevity.

A gaseous oxidant feed line 124 and outlet gas line 126 are alsoprovided, serving the same purposes as lines 24 and 26, respectively.

In operation of this embodiment, a first mixture having similarcomposition as the first mixture passing through transfer line 28 ofFIG. 1, is provided to the first sprayer 136 (FIG. 2) through the firstmixture line 132. The first mixture is atomized at the sprayer intofirst droplets 143, which remain suspended in the reaction zone 114 fora first period of time before they coalesce into a liquid 140 at thelower portion 142 of the reaction chamber 112. This first period of timedepends and can be controlled by the first droplet size, upward gaseousmovement, and other parameters. At the same time, the second mixture,passing through line 134, is also atomized by the second sprayer 138into second droplets 144. This second mixture is similar in compositionto the second mixture produced by the feed lines 16, 18, 20, and 22, asexplained in the first embodiment described above in relevance toFIG. 1. The second droplets also remain suspended in the reaction zone114 for a second period of time before they coalesce into the liquid 140at the lower portion 142 of the reaction chamber 112. This second periodof time depends and can be controlled by the second droplet size, upwardgaseous movement, and other parameters in a similar manner as the firstdroplets. Due to the inherent individuality of the droplets, themajority of the first and the second droplets do not mix before theycoalesce into the liquid 140. The liquid 140, comprising the coalescedfirst and second droplets is partially transferred to appropriateequipment (not shown) for further treatment, and partially istransferred (not shown) to the second mixture line 134 for recycling. Asthe first droplets 143 travel from the first atomizer 136 to the liquid140, they start being oxidized much faster than the second droplets 144,since they contain a higher percentage of initiator than said seconddroplets 144. In this manner both the first and the second mixture arebeing oxidized in the same reaction zone.

It is preferable that no hydrocarbon is fed to the atomizer 136 throughthe first mixture line 132, and also it is preferable that no additionalinitiator is fed to the second atomizer 138 through the second mixtureline 134.

In this arrangement, it is also preferable that any new initiator neededto replenish any oxidized or otherwise lost initiator after recycling,is added through line 115, while any new hydrocarbon needed to replenishany oxidized or otherwise lost hydrocarbon after recycling, is addedthrough line 118. Similarly, any additional catalyst and additionalsolvent should preferably be added through lines 119 and 121,respectively. Liquid 140, leaving the reaction zone through line 130 maypreferably be partially fed directly to the reaction zone 114 throughline 134 and partially fed to the same zone through line 134 afterfurther treatment.

In the different figures of the drawing, numerals differing by 100represent elements which are either substantially the same or performthe same function. Therefore, in the case that one element has beendefined once in a certain embodiment, its re-definition in otherembodiments illustrated in the figures by the same numerals or numeralsdiffering by 100 is not necessary, and it has been often omitted in theabove description for purposes of brevity.

Oxidations according to this invention, are non-destructive oxidations,wherein the intermediate oxidation product is defined as being acompound different than carbon monoxide, carbon dioxide, and a mixturethereof. Of course, small amounts of these compounds may be formed alongwith the intermediate oxidation product, which may be one product or amixture of products.

Examples include, but of course, are not limited to preparation ofaliphatic dibasic acids from the corresponding saturated cycloaliphatichydrocarbons, such as for example preparation of adipic acid fromcyclohexane.

Regarding adipic acid, the preparation of which is especially suited tothe methods and apparatuses of this invention, general information maybe found in a plethora of U.S. Patents, among other references. These,include, but are not limited to:

U.S. Pat. Nos. 2,223,493; 2,589,648; 2,285,914; 3,231,608; 3,234,271;3,361,806; 3,390,174; 3,530,185; 3,649,685; 3,657,334; 3,957,876;3,987,100; 4,032,569; 4,105,856; 4,158,739 (glutaric acid); 4,263,453;4,331,608; 4,606,863; 4,902,827; 5,221,800; and 5,321,157.

Diacids (for example adipic acid, phthalic acid, isophthalic acid,terephthalic acid, and the like) or other suitable compounds may bereacted, according to well known to the art techniques, with a thirdreactant selected from a group consisting of a polyol, a polyamine, anda polyamide in a manner to form a polymer of a polyester, or apolyamide, or a (polyamide and/or polyamideimide), respectively.Preferably the polyol, the polyamine, and the polyamide are mainly adiol, a diamine, and a diamide, respectively, in order to avoidexcessive cross-linking. The polymer resulting from this reaction may bespun by well known to the art techniques to form fibers.

Examples demonstrating the operation of the instant invention have beengiven for illustration purposes only, and should not be construed aslimiting the scope of this invention in any way. In addition it shouldbe stressed that the preferred embodiments discussed in detailhereinabove, as well as any other embodiments encompassed within thelimits of the instant invention, may be practiced individually, or inany combination thereof, according to common sense and/or expertopinion. Individual sections of the embodiments may also be practicedindividually or in combination with other individual sections ofembodiments or embodiments in their totality, according to the presentinvention. These combinations also lie within the realm of the presentinvention. Furthermore, any attempted explanations in the discussion areonly speculative and are not intended to narrow the limits of thisinvention.

All explanations given hereinabove are to be considered as speculativeand should not be construed as limiting the breadth of the claims.

All ratios are by weight.

What is claimed is:
 1. A method of preparing an intermediate oxidationproduct from a hydrocarbon comprising the steps of:(a) feeding ahydrocarbon and an initiator into a first reaction zone at a firsthydrocarbon to initiator ratio by weight; (b) oxidizing partially atleast one of said hydrocarbon and initiator to form a first mixture; (c)mixing the first mixture with a second mixture comprising the samehydrocarbon and initiator, the hydrocarbon and the initiator of thesecond mixture being present at a second hydrocarbon to initiator ratioby weight higher than the first hydrocarbon to initiator ratio, whereinthe first mixture and the second mixture are mixed at a third ratio offirst mixture to second mixture lower than 1; and (d) further oxidizingsaid hydrocarbon to a desired degree.
 2. A method of preparing anintermediate oxidation product from a hydrocarbon comprising the stepsof:(a) feeding a hydrocarbon and an initiator into a first reaction zoneat a first hydrocarbon to initiator ratio by weight; (b) oxidizingpartially at least one of said hydrocarbon and initiator to form a firstmixture; (c) mixing the first mixture with a second mixture comprisingthe same hydrocarbon and initiator, the hydrocarbon and the initiator ofthe second mixture being present at a second hydrocarbon to initiatorratio by weight higher than the first hydrocarbon to initiator ratio,wherein the first mixture and the second mixture are mixed at a thirdratio of first mixture to second mixture lower than 1; and (d) furtheroxidizing said hydrocarbon to a desired degree, wherein steps (c) and(d) are conducted in a second reaction zone different than the firstreaction zone.
 3. A method as defined in claim 1, wherein steps (a),(b), (c), and (d) are conducted in the first reaction zone.
 4. A methodas defined in claim 2, further comprising a step of introducing into atleast one of the first and the second reaction zone at least oneingredient selected from a group consisting of solvent and catalyst. 5.A method as defined in claim 3, further comprising a step of introducinginto the first reaction zone at least one ingredient selected of a groupconsisting of solvent and catalyst.
 6. A method as defined in claim 1,further comprising a step of introducing into the first reaction zone atleast one ingredient selected of a group consisting of solvent andcatalyst.
 7. A method as defined in claim 1, wherein the firsthydrocarbon to initiator ratio is in the range of 0/1 to 50/1.
 8. Amethod as defined in claim 1, wherein the second hydrocarbon toinitiator ratio is in the range of 10/1 to 1000/1.
 9. A method asdefined in claim 7, wherein the second hydrocarbon to initiator ratio isin the range of 10/1 to 1000/1.
 10. A method as defined in claim 1,wherein the initiator is a ketone, the ketone corresponding to anoxidation product of the hydrocarbon.
 11. A method as defined in claim4, wherein the solvent is an acid and the initiator is a compoundselected from a group consisting of a ketone, the ketone correspondingto an oxidation product of the hydrocarbon and an aldehyde, the aldehydebeing a reduction product of the acid.
 12. A method as defined in claim5, wherein the solvent is an acid and the initiator is a compoundselected from a group consisting of a ketone, the ketone correspondingto an oxidation product of the hydrocarbon and an aldehyde, the aldehydebeing a reduction product of the acid.
 13. A method as defined in claim6, wherein the solvent is an acid and the initiator is a compoundselected from a group consisting of a ketone, the ketone correspondingto an oxidation product of the hydrocarbon and an aldehyde, the aldehydebeing a reduction product of the acid.
 14. A method of preparing anintermediate oxidation product from a hydrocarbon comprising the stepsof:(a) feeding a hydrocarbon and an initiator into a first reaction zoneat a first hydrocarbon to initiator ratio by weight; (b) oxidizingpartially at least one of said hydrocarbon and initiator to form a firstmixture; (c) mixing the first mixture with a second mixture comprisingthe same hydrocarbon and initiator, the hydrocarbon and the initiator ofthe second mixture being present at a second hydrocarbon to initiatorratio by weight higher than the first hydrocarbon to initiator ratio,wherein the first mixture and the second mixture are mixed at a thirdratio of first mixture to second mixture lower than 1; and (d) furtheroxidizing said hydrocarbon to a desired degree; wherein the hydrocarboncomprises cyclohexane and the intermediate oxidation product comprisesadipic acid.
 15. A method as defined in claim 2, wherein the hydrocarboncomprises cyclohexane and the intermediate oxidation product comprisesadipic acid.
 16. A method as defined in claim 3, wherein the hydrocarboncomprises cyclohexane and the intermediate oxidation product comprisesadipic acid.
 17. A method as defined in claim 4, wherein the hydrocarboncomprises cyclohexane, the intermediate oxidation product comprisesadipic acid, the initiator comprises cyclohexanone, the solventcomprises acetic acid, and the catalyst comprises a cobalt compound. 18.A method as defined in claim 5, wherein the hydrocarbon comprisescyclohexane, the intermediate oxidation product comprises adipic acid,the initiator comprises cyclohexanone, the solvent comprises aceticacid, and the catalyst comprises a cobalt compound.
 19. A method asdefined in claim 6, wherein the hydrocarbon comprises cyclohexane, theintermediate oxidation product comprises adipic acid, the initiatorcomprises cyclohexanone, the solvent comprises acetic acid, and thecatalyst comprises a cobalt compound.
 20. A method as defined in claim7, wherein the hydrocarbon comprises cyclohexane, the intermediateoxidation product comprises adipic acid, the initiator comprisescyclohexanone, the solvent comprises acetic acid, and the catalystcomprises a cobalt compound.
 21. A method as defined in claim 8, whereinthe hydrocarbon comprises cyclohexane, the intermediate oxidationproduct comprises adipic acid, the initiator comprises cyclohexanone,the solvent comprises acetic acid, and the catalyst comprises a cobaltcompound.
 22. A method as defined in claim 9, wherein the hydrocarboncomprises cyclohexane, the intermediate oxidation product comprisesadipic acid, the initiator comprises cyclohexanone, the solventcomprises acetic acid, and the catalyst comprises a cobalt compound. 23.A method as defined in claim 11, wherein the acid is acetic acid and theinitiator is acetaldehyde.
 24. A method as defined in claim 12, whereinthe acid is acetic acid and the initiator is acetaldehyde.
 25. A methodas defined in claim 13, wherein the acid is acetic acid and theinitiator is acetaldehyde.
 26. A method as defined in claim 1, whereinthe hydrocarbon is an aromatic compound containing methyl groups.
 27. Amethod as defined in claim 1, wherein the hydrocarbon comprises a moietyselected from a group consisting of toluene, o-xylene, p-xylene,m-xylene and a mixture thereof, and the intermediate oxidation productcomprises a moiety selected from a group consisting of benzoic acid,phthalic acid, isophthalic acid, terephthalic acid, and a mixturethereof.
 28. A method as defined in claim 2, wherein the hydrocarboncomprises a moiety selected from a group consisting of toluene,o-xylene, p-xylene, m-xylene and a mixture thereof, and the intermediateoxidation product comprises a moiety selected from a group consisting ofbenzoic acid, phthalic acid, isophthalic acid, terephthalic acid, and amixture thereof.
 29. A method as defined in claim 3, wherein thehydrocarbon comprises a moiety selected from a group consisting oftoluene, o-xylene, p-xylene, m-xylene and a mixture thereof, and theintermediate oxidation product comprises a moiety selected from a groupconsisting of benzoic acid, phthalic acid, isophthalic acid,terephthalic acid, and a mixture thereof.
 30. A method as defined inclaim 1, wherein a catalyst is added in at least step (a).
 31. A methodas defined in claim 2, further comprising a step of introducing acatalyst into at least the first reaction zone.
 32. A method as definedin claim 3, further comprising a step of introducing a catalyst into thefirst reaction zone.
 33. A method as defined in claim 30, wherein asolvent is added in at least step (c).
 34. A method as defined in claim31, further comprising a step of introducing a solvent into at least thefirst reaction zone.
 35. A method as defined in claim 32, furthercomprising a step of introducing a solvent into the first reaction zone.36. A method as defined in claim 1, wherein the first mixture and thesecond mixture are mixed at a third ratio of first mixture to secondmixture lower than
 1. 37. A method as defined in claim 36, wherein thethird ratio is in the range of 1/5 to 1/500.
 38. A method as defined inclaim 37, wherein the third ratio is in the range of 1/10 to 1/200. 39.A method as defined in claim 38, wherein the third ratio is in the rangeof 1/20 to 1/100.
 40. A method as defined in claim 1, wherein the firstmixture in the first reaction zone undergoes a conversion to oxidationproducts in the range of 5-90%.
 41. A method as defined in claim 39,wherein the first mixture in the first reaction zone undergoes aconversion to oxidation products in the range of 10-80%.
 42. A method asdefined in claim 40, wherein the first mixture in the first reactionzone undergoes a conversion to oxidation products in the range of20-60%.
 43. A method as defined in claim 7, wherein the third ratio isin the range of 1/20 to 1/100, and wherein the first mixture in thefirst reaction zone undergoes a conversion to oxidation products in therange of 20-60%.
 44. A method as defined in claim 8, wherein the thirdratio is in the range of 1/20 to 1/100, and wherein the first mixture inthe first reaction zone undergoes a conversion to oxidation products inthe range of 20-60%.
 45. A method as defined in claim 9, wherein thethird ratio is in the range of 1/20 to 1/100, and wherein the firstmixture in the first reaction zone undergoes a conversion to oxidationproducts in the range of 20-60%.
 46. A method as defined in claim 17,wherein the third ratio is in the range of 1/20 to 1/100, and whereinthe first mixture in the first reaction zone undergoes a conversion tooxidation products in the range of 20-60%.